Full-mesh optical backplane with standard MM fiber ribbons.

In this work an optical backplane prototype exploiting standard MM 12-fiber ribbons has proved a full-mesh optical connection between 8 boards, that is, each board provides bidirectional connections with each of the other boards. The optoelectronic boards are equipped with 8 pairs of MPO connectors, each pair (TX and RX) enclosed in a protective casing to ensure robustness during board insertion (Fig.1). The proposed technological solution, which relies on a patent-pending layout routing of optical connections, is modular. The optical backplane is in fact constituted by a frame, conform to ATCA standard structural specifications, divided into 8 subracks (one shown in Fig. 2) transversal to the 8 optoelectronic boards. The automated assembly of subracks, has been patented by CNR-ITIA [5]. The proposed layout thus offers the possibility of arbitrarily dividing the backplane into submodules for the use of different machines and allows easy maintenance of the backplane in case of breakage or replacement of optical connectors. Validation of the prototype was carried out with boards equipped with AVAGO miniPOD transceivers (12-MM-850nm-VCSEL arrays @10 Gb/s) to achieve 1Tb/s overall bandwidth. System characterizations demonstrated good performance with overall power loss due to fiber ribbon bending and insertion loss < 2 dB, eligible with 4.8 dB link power budget, and no penalty @ 10-12 BER with respect to back-to-back in each channel (Fig. 2). The advantages of the approach adopted in the design and implementation of this backplane are the automated assembly of off-the-shelf components (standard MM fiber ribbons) and a completely full-mesh bandwidth-upgradable optical interconnection. These features make this solution competitive for datacenters applications with respect to existing electrical backplane and even also to optical backplane based on tailored fiber ribbon sheets [3].